


My colours in your heart.

by RussianSunflower3



Series: Seijou 4 Week; Sunflower style [12]
Category: Haikyuu!!
Genre: Alternate Universe - Soulmates, M/M, Mostly Fluff, Polyamory, Seijou 4 Week, Tiny weeny little drop of angst
Language: English
Status: Completed
Published: 2017-01-31
Updated: 2017-01-31
Packaged: 2018-09-21 03:07:00
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,188
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/9529094
Author URL: https://archiveofourown.org/users/RussianSunflower3/pseuds/RussianSunflower3
Summary: Everybody has a heart that pulses and glows with their own unique colour.When they find a soulmate, their colours unite and a heart beats with as many colours as lifetimes loved.





	

For as long as he can remember, his heart has always thrummed with a steady sky blue glow, luminescent even through multiple layers of clothing. The neon pulses in iambic pentameter, a representation of his heartbeat. In the darkest nights, as his room flashes and throbs with the bursts of blue glow, he taps along with his fingers on the mattress. 

He wonders what other colour, or _colours_ , will be joining him.

Matsukawa would like to think his soulmate will fill half his heart with a complementary colour, like yellow or pink. Maybe even white. The colours have no particular meaning, only that each person has their own colour thrumming in their chest, visible through clothing and bedcovers and any transparent or translucent object. Sometimes, when he’s having strong emotions, the glow of his heart spreads along veins and arteries, but never beyond his chest.

Some people had already found their soulmates. When soulmates touched, the neon glow would flow through their arteries towards the point of contact, and then into their partner’s veins via electromagnetics. Their colour would travel to their soulmates heart and fill a half, a third, a quarter… However many soulmates they had, the heart would equally split into colours for each.

But at 14, Matsukawa still had a heart of pure blue. He’d never even had the slight sparks that flew off contact with a good friend. He was lonely. He had the feeling, however, that this was about to change. His first day of high school saw him standing outside the gymnasium, ready to walk in and introduce himself as a new member of the volleyball club. Perhaps, in his teammates, he could find friends of his own. Or even a _soulmate_. After all, his ideal soulmate would like volleyball!

“Are you gonna go in or just stand there blocking the door?” Matsukawa jumps and looks over his shoulder, spotting two people - probably first years like him - waiting for him to move. Sheepishly, he stepped aside, rubbing the back of his head.

“Uh, yeah. Sorry, I was just thinking.” The one with black, spiky hair, green eyes, and a grey pulsing heart raises an eyebrow in question, whilst his brunette amber pulsing heart friend grins slyly.

“Hmmm~? Must have been something S _uuuuu_ per interesting!”

“Oikawa, don’t bother him.” As green-eyes elbows the boy named Oikawa, there’s golden sparks and their hearts flash, grey and amber streaking towards each other. The contact is too quick for the colours to bleed into each others hearts, and Matsukawa understands that whilst they’ve _found_ their soulmates, they’re not solidifying anything yet. School has to come first.

“Just volleyball thoughts.” Oikawa perks up instantly.

“Definitely interesting then! What position do you play? I’m setter!” Matsukawa blinks at how bright and forward Oikawa is, but breaks into a smile. Oikawa is as warm and welcoming as his amber heart. 

“Middle Blocker. What about you?” The last of his statement is directed towards the black haired boy, his grey heart throbbing soft and slow. He must be content, even if the stern frown on his face doesn’t show it.

“Wing Spiker. I’m Iwaizumi Hajime, by the way. This idiot is Oikawa Tooru.” Matsukawa nods respectfully at them.

“Matsukawa Issei. Pleased to meet you.” He reaches out to shake their hands, but before they can respond in any way, he drops it. Coming into high school, he vowed not to make physical contact with anyone before he _knew_ them. He won’t be like those people that rush into a relationship just because their colours told them so. Iwaizumi clears his throat and gestures towards the open gymnasium doors.

“So…”

“Let’s go~!” With a leap of joy, Oikawa practically skips into the gym. Iwaizumi shakes his head, sighing with fondness. There’s truly love gleaming in his eyes and his grey glow skips a beat as his heart does the same. The corner of Matsukawa’s lips twitch upwards. He wonders when they found out they were soulmates, and how long they knew each other beforehand. They seem close. Really close.

“I’d better stop his Royal Stupidness from causing a riot in there.” Iwaizumi brushes past him, but Matsukawa doesn’t step back in time and their hands brush. Because he’s looking into the gym, Iwaizumi doesn’t see the sparks of bronze and the sky blue spreading up his fingertips for a moment. But Matsukawa does. Eyes wide, he stares at his own hand until the pale grey, like storm clouds and wisps of smoke, fades from his fingertips. 

“What the heckie…” He blinks at his hands in betrayal, before wiping them off on his trousers and entering the gym. Iwaizumi didn’t see, so he’ll just have to avoid physical contact as much as humanly possibly until he’s comfortable enough to let Iwaizumi know. Oikawa too, of course, since he and Iwaizumi are already soulmates. Once they’ve changed, the three new first years step into line, their senpai casting a gaze over the 7 prospective new members.

“Alright, listen up! We’re gonna have a practice match to see if you newbies have the skill to make the team! Let’s see… I want the three with least experience on this side of the net, and four with most experience on the other. We’ll make up the rest of the numbers.” 

“Iwa-chan! We’re on the side with four!” A freckled boy with light blond hair and red soulglow nervously shuffles over to two companions, both with dark hair and different shades of green hearts glowing. There’s only one more prospective first year left, and Matsukawa takes one look at him before his lungs seize and he forgets how to breath.

He’s beautiful.

He’s _stunning_.

Okay, he’s not the stereotypical classification of ‘beauty’ that society demands, but there’s something about him that just steals all the air from Matsukawa’s personal bubble and practically _shines_. His heart glows with a gentle shade of lavender, as pastel and unique as his pinkish hair. Matsukawa’s never seen a purple heart before. 

“Mattsun!!! Come and meet Makki!” 

“It’s _Hana_ maki, Trashykawa. You should have learnt that in the past three years!” Oikawa lets out a humourous noise as a volleyball lightly smacks the back of his head. Hanamaki - _Hanamaki_ , what a fittingly beautiful name! - laughs unabashed and moves to pick up a stray, rolling volleyball.

“Hey Iwaizumi, take another shot, I don’t think you knocked common sense into him yet!”

“Oh hahaha- _No, Iwa-chan! Don’t take his suggestion seriously_!” Iwaizumi breaks off with a warm chuckle as he drops his arm, having only been posing as if he were about to throw another one. Matsukawa huffs in amusement, and that’s when he realises brown eyes are looking at him with a glimmer of happiness. 

“Hey, I’m Hanamaki Takahiro. What about you, stranger?”

“Matsukawa Issei…” He barely gets his voice out, sounding as if it’s being drawn from him like the breath from his lungs, a soft exhale in Hanamaki’s direction that Hanamaki only just hears.

“Pfff-! Quiet one? That seems to fit you well!” Matsukawa raises a thick eyebrow, the corner of his eyes creasing in challenge.

“Oh believe me, I am _not_. It’s just because I don’t want to scare you off.” Hanamaki laughs.

“Scare _me_ off? I’d like to see you try!” He winks and sticks his tongue out before jogging over to join Iwaizumi and Oikawa warming up on the court. Matsukawa’s glowing heart skips a beat. Two beats. And then it races, the sky blue contrasting the cherry red of his cheeks nicely. He clutches his hand over it tightly, wondering if he should have put something opaque over his chest to stop his heart being visible. He’ll consider that tomorrow.

“Mattsun, c’mon! We have to beat Yudacchi and Sawauchi-kun and Shido-chan!” The three with less experience are on the other side of the net, backed up by the third years, whilst Oikawa’s side has two second years to make up for their lack of players. Oikawa stands in the setter position, positively gleaming, and Matsukawa is sure his amber heart beats a little quicker on the court than in general. He truly loves the game.

The first ball goes to Iwaizumi, and there’s a silence of awe on the court after the boy spikes it down so hard that it bounces into the basketball nets behind the court. Iwaizumi lands steadily and pumps his fist into the air with a shout of victory, Oikawa jumping forwards and pulling him into a rapid hug, enough to be a celebration, but not enough for their hearts to fill with each others colours, golden sparks flying off like sparklers. 

“Iwaizumi, that was awesome!!!” Hanamaki grins and gives him a thumbs up, and Matsukawa quickly shakes off his amazement to congratulate Iwaizumi on a point well-earned. When all four of them are in a circle, smiling at each other and spurning each other on, Matsukawa can’t help but feel like he finally has some close friends - and he’s going to fit right in.

Matsukawa isn’t wrong. 

Three months pass by smoothly, and the quartet are closer than ever. Oikawa and Iwaizumi announce that they’re waiting until third year to take on each others colours, and only if they’re ready. Hanamaki nods, unusually serious, and says it’s best for them not to rush into things. Matsukawa wonders if he’s seen worrisome things happening to those who _do_ rush into it.

Then things change. Dramatically. It’s just a normal day, sitting in Iwaizumi’s classroom eating lunch, when Hanamaki challenges him to an arm wrestling match. Always the competitive type, Iwaizumi rolls up his sleeve and places his elbow on the table.

“Go Iwa-chan! You’ll definitely win~! Right, Mattsun?”

“Hmmm~... I think I’ll cheer for the underdog, actually.”

“Who are you calling _underdog_?!” He laughs as Hanamaki playfully glares at him, sticking his hands on his hips and leaning back against the wall to watch. Iwaizumi makes a show of flexing his arm, parading his muscles and then shuffling seriously into position. He narrows his eyes at Hanamaki, a mischievous glint amongst the swirling green, grey glow from his heart reflecting in his eyes.

“Come at me, weakling~.” Hanamaki leans over and links their hands and-

Bright, silver sparks. Lavender and grey spreading to reach other, hands pulled away at the last second and the colours dissipating back to their original hearts. Iwaizumi and Hanamaki stare at each other as Matsukawa and Oikawa stare at _them_. 

Hanamaki is deeply surprised, but there’s little more in his expression than that. Iwaizumi looks… Hurt. Deeply hurt, as if his own heart has betrayed him. 

“I- I have to go.” He grabs his bag and bolts before the others can react, and when they do, Oikawa only shouts for Iwaizumi to wait. He glances desperately to Matsukawa, and despite knowing that _he_ had bronze sparks with Iwaizumi before when they accidentally brushed, Matsukawa breaks into a run after Iwaizumi. He leaves Hanamaki and Oikawa to talk, and most likely, see if there’s a soulglow reaction between them too.

“Iwaizumi! _Iwaizumi!_ ” His outside shoes are still in his shoe locker. Either Iwaizumi left with his indoor shoes or- 

He’s still in the building. Still on school grounds. Matsukawa turns and heads towards the gymnasium. Sure enough, one of the doors is ajar and he can hear the distinctive sound of a volleyball smacking aggressively against the ground, reverbing off a wall and being spiked harshly again with a guttural shout. Iwaizumi must be spiking the ball against the wall until he drops it. Matsukawa eases through the door, quietly approaching until Iwaizumi notices him out the corner of his eye.

“What are you doing here…?”

“Came to check on you. You alright?” Iwaizumi lets the ball drops and then falls to sit on the wooden floor cross-legged. He looks a little lost.

“I don’t- I don’t understand. I love _Oikawa_. I’ve always loved Oikawa! Why- Why is my heart reacting to Hanamaki?!” Matsukawa blinks. 

“Iwaizumi… You do know you can more than one soulmate, right?”

“What?” He blinks at Matsukawa with such innocent confusion, that Matsukawa actually laughs, although he feels guilty when Iwaizumi turns his gaze to the floor with a frown of tension.

“Oh, Iwaizumi. Let good ol’ Issei explain it to ya.” He drops to the floor in front of Iwaizumi, a gangle of awkward limbs that he rearranges into lying on his front, chin in his hands with his elbows on the floor, and ankles crossed over each other in the air with his knees at a 45 degree angle-ish. Iwaizumi hunches over in something akin to defeat, probably feeling a little sheepish or stupid, and listens as Matsukawa explains poly-bonds.

By the end of the talk, Iwaizumi is clutching at his shirt, fingers scrunching the material that still lets a steady grey thrum pulse through. He’s thinking, deep and hard.

“So-...” Matsukawa waits whilst he tries to find the words.

“So I have a poly-bond with Oikawa _and_ Hanamaki? B-But… I don’t understand…”

“Hmm? Did I not explain it right?” The tips of Iwaizumi’s ears turn red and his heart beats faster.

“N-no, just… I like Hanamaki differently to Oikawa… I know I love Oikawa, but- but I never thought about Hanamaki like that before. I- I like Hanamaki… Closer to the way I like you…” Matsukawa splutters, because he knows exactly what that means.

Iwaizumi likes him, like he likes Hanamaki. And that probably means that the reaction from the first day they met _isn’t_ just a one-sided coincidence. Taking in a deep breath, Matsukawa holds his hand out flat.

“Do you want to try it?” Iwaizumi looks at it, biting his bottom lip in thought. He shakily raises his own hand, hovering mere millimeters above skin contact.

“You don’t have to, if you don’t want to.”

“... I have to know.” He presses his palm flat against Matsukawa’s, and bronze sparks fly as grey and sky blue rush to meet each other, tingling colour in their fingertips. They snatch their hands away before the paths to their hearts can be completed, both of them left with each others colour lingering in their hands and up their forearms. 

“So now you know.” Iwaizumi stares as the smoke of sky blue dissipates in his skin, the light glow becoming fainter as it fades. His own grey glow fades into Matsukawa’s skin, and they’re left sitting there in silence, a heart of grey and a heart of blue, facing each other and beating a split second out of sync. 

“Now I know.” Matsukawa is about to ask Iwaizumi what he’s going to do, when the gym doors burst open, Oikawa and Hanamaki running in and jogging over to them with bright smiles.

“Iwa-chan! Iwa-chan, we’re a poly-bond! You, me ‘n’ Makki!” Iwaizumi’s eyes flicker to Matsukawa for a moment, and Oikawa doesn’t miss it, head tilting to the side inquisitively. 

“It’s more than that, actually. Our- Our bond is you, me, Hanamaki _and_ Matsukawa.” Oikawa squeals and claps his hands, celebrating because he thought he’d felt something with Matsukawa too. In the meantime, Hanamaki pokes Matsukawa’s shoulder. Bronze sparks fly and their colours show on each others skin for three or four seconds.

“Wait, so… How come Iwaizumi and Oikawa have golden sparks… You have bronze sparks with all of us… But I have _silver_ with them?” The corner of Matsukawa’s lips twitch upwards.

“It’s an indicator of how long you’ve known the person. Bronze turns to silver at a year, silver turns to gold at a decade, gold turns to magnesium white if soulmates have known each other over a century, but that’s incredibly rare. Usually only soulmates who’ve known each other since birth.”

“Ohhh.. That makes sense… We went to Kitagawa together, so it’s… Just over three years.”

“Iwa-chan and I know each other from toddlers! So that’s, uh, lemme count…” Iwaizumi rolls his eyes, pressing a swift kiss to Oikawa’s cheek.

“12 years.” 

“I knew that, it was on the tip of my tongue!” Hanamaki snickers at their interaction as Matsukawa rolls his eyes with amusement and Iwaizumi exchanges quips with Oikawa about his math skills.

“You guys do know we still have a lesson left of the day, right?” As Matsukawa speaks, the bell to end lunch rings and they jump to their feet, racing through the hallways to get back to the main building before they’re deemed late students.

Time passes. Years change. Matsukawa’s bronze touch turns to silver in second year, and when they reach third year, Oikawa is announced the new captain. It’s the day after when he and Iwaizumi walk into the gymnasium, Oikawa beaming and Iwaizumi blushing, their colours distinctively changed.

Iwaizumi’s smokey grey heart now has a quarter of amber. Oikawa’s amber heart has a quarter or grey. Hanamaki bursts out laughing when they still have lingering colour on each others lips, and their hands are joined together with continuous golden sparkles falling from them like glitter. 

“Makki, Mattsun! Get over here! I want to give you my beautiful bright glow too!” They look at each other first, settling into soft smiles as Matsukawa drops the volleyball in his hands, instead interlocking his fingers with Hanamaki as they walk over to Iwaizumi and Oikawa. Lavender and sky blue dance along their fingers and trail up their arms, bleeding into each others hearts in beautiful wisps and swirls. 

As soon as their quarters are complete, Hanamaki leaps towards Oikawa and Iwaizumi, knocking them to the floor and dragging Matsukawa down with him. In a jumbled heap, laughing at their tangled limbs and warm dog-pile, their colours all meet and they pull away with a quarter of hearts in each other.

Sky blue, Grey, Lavender, and Amber. It doesn’t matter that it wasn’t the white that Matsukawa thought about, or even yellow or pink. They’re beautiful as they are, more beautiful that he could ever imagine, and warmer than he could ever believe. Their colours are love, and they settle in his heart in four equal parts, beating in perfect sync. 

He looks at the others, and whilst their colours are in different places, they _all_ beat in sync. Oikawa looks up at them with glistening, watery eyes that burn with determination, and they groan because they just know it’s going to be something volleyball related.

“You know… We’re going to kick ass on the court together. We’re going to be the strongest team. We’ll go down in history as the third years that worked in perfect harmony.” Iwa nudges his shoulder, lips almost brushing Matsukawa’s ear from where he’s still lying atop him.

“On court, _and_ off.” They giggle their agreement, but before anything more can be said, there’s voices outside the gym and they quickly untangle before the door opens, the second years walking in. Blissfully unaware they were interrupting anything, Yahaba holds up a stack of paperwork.

“Are we ready to look over the new applicant forms?” Oikawa looks at his vice captain, at Hanamaki, and Matsukawa, and they nod in return, hearts pulsing with a bright glow of determination. 

“We’re ready~.”

**Author's Note:**

> What colour would your heart be?


End file.
